There is a known conventional technique for decomposing speech signals into periodic components and aperiodic components that is called pitch-scaled harmonic filtering (PSHF).
For example, “Pitch-Scaled Estimation of Simultaneous Voiced and Turbulence-Noise Components in Speech”, IEEE Trans. Speech and Audio Processing, vol. 9, pp. 713-726, October 2001 (P Jackson) discloses a technique of extracting a waveform from periodic waveforms by windowing using an analysis window having a window width that is N times a fundamental period, of performing a discrete Fourier transformation (DFT) on the extracted waveform using the window width as an analysis length, and of separating components into periodic and aperiodic components by using the characteristic that harmonic components appear in synchronization with frequency bins at integral multiples of N.